Decommissioning Trust Funds (Available For Sale Securities Continuous Unrealized Loss Position Fair Value) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 12 months Fair Value		$ 8.0
More than 12 months Fair Value		0.0
Total Fair Value		8.0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		1.0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0.0
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		1.0
Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 12 months Fair Value	$ 1,691.0	1,099.0
More than 12 months Fair Value	357.0	265.0
Total Fair Value	2,048.0	1,364.0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	33.0	7.0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	18.0	9.0
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	51.0	16.0
Entergy Arkansas [Member] | Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 12 months Fair Value		0.0
More than 12 months Fair Value		0.0
Total Fair Value		0.0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		0.0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0.0
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		0.0
Entergy Arkansas [Member] | Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 12 months Fair Value	259.7	168.0
More than 12 months Fair Value	78.2	41.4
Total Fair Value	337.9	209.4
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	6.8	1.2
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	4.1	1.8
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	10.9	3.0
Entergy Louisiana [Member] | Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 12 months Fair Value		0.0
More than 12 months Fair Value		0.0
Total Fair Value		0.0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		0.0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0.0
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		0.0
Entergy Louisiana [Member] | Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 12 months Fair Value	355.6	135.3
More than 12 months Fair Value	74.0	84.4
Total Fair Value	429.6	219.7
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	5.8	1.1
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	3.5	2.5
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	9.3	3.6
System Energy [Member] | Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 12 months Fair Value		0.0
More than 12 months Fair Value		0.0
Total Fair Value		0.0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		0.0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0.0
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		0.0
System Energy [Member] | Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 12 months Fair Value	267.6	196.9
More than 12 months Fair Value	34.3	10.4
Total Fair Value	301.9	207.3
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	5.2	1.0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1.9	0.2
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 7.1	$ 1.2